9aed02feae
After emulating an unaligned access in delay slot of a branch, we pretend as the delay slot never happened - so return back to actual branch target (or next PC if branch was not taken). Curently we did this by handling STATUS32.DE, we also need to clear the BTA.T bit, which is disregarded when returning from original misaligned exception, but could cause weirdness if it took the interrupt return path (in case interrupt was acive too) One ARC700 customer ran into this when enabling unaligned access fixup for kernel mode accesses as well Cc: stable@vger.kernel.org Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
267 lines
6.4 KiB
C
267 lines
6.4 KiB
C
/*
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* Copyright (C) 2011-2012 Synopsys (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* vineetg : May 2011
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* -Adapted (from .26 to .35)
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* -original contribution by Tim.yao@amlogic.com
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*
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*/
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#include <linux/types.h>
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#include <linux/perf_event.h>
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#include <linux/ptrace.h>
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#include <linux/uaccess.h>
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#include <asm/disasm.h>
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#ifdef CONFIG_CPU_BIG_ENDIAN
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#define BE 1
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#define FIRST_BYTE_16 "swap %1, %1\n swape %1, %1\n"
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#define FIRST_BYTE_32 "swape %1, %1\n"
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#else
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#define BE 0
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#define FIRST_BYTE_16
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#define FIRST_BYTE_32
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#endif
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#define __get8_unaligned_check(val, addr, err) \
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__asm__( \
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"1: ldb.ab %1, [%2, 1]\n" \
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"2:\n" \
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" .section .fixup,\"ax\"\n" \
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" .align 4\n" \
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"3: mov %0, 1\n" \
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" j 2b\n" \
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" .previous\n" \
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" .section __ex_table,\"a\"\n" \
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" .align 4\n" \
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" .long 1b, 3b\n" \
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" .previous\n" \
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: "=r" (err), "=&r" (val), "=r" (addr) \
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: "0" (err), "2" (addr))
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#define get16_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v, a = addr; \
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__get8_unaligned_check(v, a, err); \
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val = v << ((BE) ? 8 : 0); \
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__get8_unaligned_check(v, a, err); \
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val |= v << ((BE) ? 0 : 8); \
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if (err) \
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goto fault; \
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} while (0)
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#define get32_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v, a = addr; \
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__get8_unaligned_check(v, a, err); \
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val = v << ((BE) ? 24 : 0); \
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__get8_unaligned_check(v, a, err); \
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val |= v << ((BE) ? 16 : 8); \
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__get8_unaligned_check(v, a, err); \
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val |= v << ((BE) ? 8 : 16); \
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__get8_unaligned_check(v, a, err); \
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val |= v << ((BE) ? 0 : 24); \
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if (err) \
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goto fault; \
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} while (0)
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#define put16_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v = val, a = addr;\
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\
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__asm__( \
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FIRST_BYTE_16 \
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"1: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"2: stb %1, [%2]\n" \
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"3:\n" \
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" .section .fixup,\"ax\"\n" \
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" .align 4\n" \
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"4: mov %0, 1\n" \
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" j 3b\n" \
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" .previous\n" \
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" .section __ex_table,\"a\"\n" \
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" .align 4\n" \
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" .long 1b, 4b\n" \
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" .long 2b, 4b\n" \
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" .previous\n" \
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: "=r" (err), "=&r" (v), "=&r" (a) \
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: "0" (err), "1" (v), "2" (a)); \
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\
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if (err) \
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goto fault; \
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} while (0)
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#define put32_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v = val, a = addr;\
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\
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__asm__( \
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FIRST_BYTE_32 \
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"1: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"2: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"3: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"4: stb %1, [%2]\n" \
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"5:\n" \
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" .section .fixup,\"ax\"\n" \
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" .align 4\n" \
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"6: mov %0, 1\n" \
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" j 5b\n" \
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" .previous\n" \
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" .section __ex_table,\"a\"\n" \
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" .align 4\n" \
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" .long 1b, 6b\n" \
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" .long 2b, 6b\n" \
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" .long 3b, 6b\n" \
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" .long 4b, 6b\n" \
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" .previous\n" \
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: "=r" (err), "=&r" (v), "=&r" (a) \
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: "0" (err), "1" (v), "2" (a)); \
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\
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if (err) \
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goto fault; \
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} while (0)
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/* sysctl hooks */
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int unaligned_enabled __read_mostly = 1; /* Enabled by default */
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int no_unaligned_warning __read_mostly = 1; /* Only 1 warning by default */
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static void fixup_load(struct disasm_state *state, struct pt_regs *regs,
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struct callee_regs *cregs)
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{
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int val;
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/* register write back */
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if ((state->aa == 1) || (state->aa == 2)) {
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set_reg(state->wb_reg, state->src1 + state->src2, regs, cregs);
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if (state->aa == 2)
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state->src2 = 0;
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}
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if (state->zz == 0) {
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get32_unaligned_check(val, state->src1 + state->src2);
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} else {
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get16_unaligned_check(val, state->src1 + state->src2);
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if (state->x)
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val = (val << 16) >> 16;
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}
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if (state->pref == 0)
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set_reg(state->dest, val, regs, cregs);
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return;
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fault: state->fault = 1;
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}
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static void fixup_store(struct disasm_state *state, struct pt_regs *regs,
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struct callee_regs *cregs)
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{
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/* register write back */
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if ((state->aa == 1) || (state->aa == 2)) {
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set_reg(state->wb_reg, state->src2 + state->src3, regs, cregs);
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if (state->aa == 3)
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state->src3 = 0;
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} else if (state->aa == 3) {
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if (state->zz == 2) {
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set_reg(state->wb_reg, state->src2 + (state->src3 << 1),
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regs, cregs);
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} else if (!state->zz) {
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set_reg(state->wb_reg, state->src2 + (state->src3 << 2),
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regs, cregs);
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} else {
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goto fault;
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}
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}
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/* write fix-up */
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if (!state->zz)
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put32_unaligned_check(state->src1, state->src2 + state->src3);
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else
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put16_unaligned_check(state->src1, state->src2 + state->src3);
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return;
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fault: state->fault = 1;
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}
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/*
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* Handle an unaligned access
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* Returns 0 if successfully handled, 1 if some error happened
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*/
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int misaligned_fixup(unsigned long address, struct pt_regs *regs,
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struct callee_regs *cregs)
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{
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struct disasm_state state;
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char buf[TASK_COMM_LEN];
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/* handle user mode only and only if enabled by sysadmin */
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if (!user_mode(regs) || !unaligned_enabled)
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return 1;
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if (no_unaligned_warning) {
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pr_warn_once("%s(%d) made unaligned access which was emulated"
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" by kernel assist\n. This can degrade application"
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" performance significantly\n. To enable further"
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" logging of such instances, please \n"
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" echo 0 > /proc/sys/kernel/ignore-unaligned-usertrap\n",
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get_task_comm(buf, current), task_pid_nr(current));
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} else {
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/* Add rate limiting if it gets down to it */
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pr_warn("%s(%d): unaligned access to/from 0x%lx by PC: 0x%lx\n",
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get_task_comm(buf, current), task_pid_nr(current),
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address, regs->ret);
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}
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disasm_instr(regs->ret, &state, 1, regs, cregs);
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if (state.fault)
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goto fault;
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/* ldb/stb should not have unaligned exception */
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if ((state.zz == 1) || (state.di))
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goto fault;
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if (!state.write)
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fixup_load(&state, regs, cregs);
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else
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fixup_store(&state, regs, cregs);
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if (state.fault)
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goto fault;
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/* clear any remanants of delay slot */
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if (delay_mode(regs)) {
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regs->ret = regs->bta ~1U;
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regs->status32 &= ~STATUS_DE_MASK;
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} else {
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regs->ret += state.instr_len;
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/* handle zero-overhead-loop */
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if ((regs->ret == regs->lp_end) && (regs->lp_count)) {
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regs->ret = regs->lp_start;
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regs->lp_count--;
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}
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}
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perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, address);
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return 0;
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fault:
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pr_err("Alignment trap: fault in fix-up %08lx at [<%08lx>]\n",
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state.words[0], address);
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return 1;
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}
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